The vacillating spirit of McClellan is alive today in the Democratic Party's leadership
I keep finding echoes of those histories in the present day. The biggest I see is with how both leaders and common people in the North radically reframed their understanding of the war as it went along. Lincoln's first inaugural speech, coming hot on the heels of secession, promised the South that he would not interfere with slavery where it currently existed. His second inaugural, coming as victory in the war was in sight, deemed slavery a moral evil and the Civil War as God's punishment on a guilty nation.
I see a parallel in the ways that those Americans opposed to Trump, who is a political descendant of the Confederacy, are fighting him. Some understand that this is a fight where the enemy is simply not going to give up or play fair. They also know that the only forward is not getting back to the way it used to be, but to have, in the words of Lincoln at Gettysburg, a "new birth of freedom." Politicians like Elizabeth Warren, Bernie Sanders, Alexandra Ocasio-Cortez, and others seem to get this.
On the other hand, there are plenty of modern day McClellans. George McClellan was able to organize the Army of the Potomac into a disciplined fighting force, but was unwilling to actually USE that force. He was also contemptuous of the notion that the war was about anything other than restoring the Union, and when he ran for president in 1864 that included the willingness to allow the South back into the Union without the elimination of slavery.
The parallels are not absolute, but I see a lot of McClellan in Nancy Pelosi, Chuck Schumer, and other Democratic Party leaders. Their current strategy is simply to wait Trump out. Like McClellan refusing to advance in the Peninsula Campaign when he had the advantage, they think by not fighting they will somehow win, and that fighting is too much of a risk. So they sit on their hands, and refuse to impeach a president who only responds with more violations of the Constitution. They attack the left wing of their own party, fearing that they will alienate a few retired white auto workers in Ohio while ignoring the masses of people of color, and youth of all races who support their policies but often feel alienated from the party.
The Union army finally emerged victorious under the leadership of Grant, who understood that winning was going to require more sacrifice and more fighting. It meant fighting a different kind of war, one whose intensity matched what the situation demanded. When his methods came under criticism, Lincoln defended him, declaring that "he fights." Grant himself understood that the Union's fearful, defensive posture needed to stop. He famously told his generals soon after taking command that they needed to stop worrying about what Robert E Lee was going to do to them, but what THEY were going to do to Robert E Lee.
That's something that the Democratic leadership could learn from. The Republican caucus is full of members like Gohmert and Gaetz who are FAR more outside of the political mainstream than folks like Ocasio-Cortez. Expanded health care, legal abortion, gun control, subsidized child care, and debt relief are all popular positions. Democrats need to run proudly on these positions and take the fight to the other side. If the current leadership does not understand that reality, they need to get out of the way.